Synthesis, characterization and photocatalytic activity of AgBr/H2WO4 composite photocatalyst

Enhanced Photodegradation of Synthetic Dyes Mediated by Ag3PO4-Based Semiconductors under Visible Light Irradiation

Four silver phosphate-based materials were successfully synthesized, characterized, and evaluated, together with TiO2, in the photodegradation of synthetic dyes (tartrazine, Orange II, rhodamine, and Brilliant Blue FCF) under two irradiation sources centered at 420 and 450 nm. Scanning Electron Microscopy (SEM) images showed different topologies of the synthesized materials, whereas diffuse reflectance spectra demonstrated that they display absorption up to 500 nm. Degradation experiments were performed in parallel with the silver materials and TiO2. Upon irradiation centered at 420 nm, the abatement of the dyes was slightly more efficient in the case of TiO2—except for Orange II. Nevertheless, upon irradiation centered at 450 nm, TiO2 demonstrated complete inefficiency and silver phosphates accomplished the complete abatement of the dyes—except for Brilliant Blue FCF. A careful analysis of the achieved degradation of dyes revealed that the main reaction mechanism involves electron transfer to the photogenerated holes in the valence band of silver photocatalysts, together with the direct excitation of dyes and the subsequent formation of reactive species. The performance of TiO2 was only comparable at the shorter wavelength when hydroxyl radicals could be formed; however, it could not compete under irradiation at 450 nm since the formed superoxide anion is not as reactive as hydroxyl radicals.

Fabrication of a Z-scheme AgBr/Bi4O5Br2 nanocomposite and its high efficiency in photocatalytic N2 fixation and dye degradation

Z-scheme AgBr/Bi₄O₅Br₂ nanocomposite was synthesized via a simple ion-exchange method and firstly applied in photocatalytic N₂ fixation under simulated sunlight.

A label-free aptamer-based cytosensor for specific cervical cancer HeLa cell recognition through a g-C3N4-AgI/ITO photoelectrode

Facile and efficient detection of cancer cells in the early phases of the disease is one of the main challenges in cancer diagnostics. It has been found that photoactive materials and bio-recognition elements are two key factors in the development of promising photoelectrochemical (PEC) biosensors for cancer cell detection, which can play significant roles for realizing early cancer diagnostics with high sensitivity and selectivity. In this study, we designed a novel label-free PEC aptamer-based cytosensor for the specific detection of cancer cells such as HeLa cells by using water-dispersible g-C₃N₄-AgI nanocomposites as visible light-sensitive materials and anti-CEM/PTK7 aptamer as the bio-recognition element. It was observed that when a suitable amount of AgI nanoparticles was doped in two-dimensional graphite-like carbon nitride nano-sheets (g-C₃N₄ NSs), the visible light photocurrent response could be significantly improved. The PEC response of the as-prepared biosensor based on the g-C₃N₄-AgI/ITO photoelectrode was linearly proportional to the relevant cancer cells such as HeLa cells at concentrations ranging from 10 to 10⁶ cells per mL with a limit of detection of 5 cells per mL. In addition, the g-C₃N₄-AgI/ITO photoelectrode and the fabricated cytosensor exhibited long-term stability, good reproducibility, excellent selectivity, and high sensitivity, demonstrating the successful conjugation of g-C₃N₄-AgI NSs with the aptamer and target cancer cells in the high performance PEC cytosensor.

Double Effect Electron Transfer System in the AgBr/ZnO Composite with Enhanced Photocatalytic Degradation Performance against 3-Chlorophenol under Visible Light Irradiation

Visible light-driven novel and highly efficient AgBr/ZnO photocatalysts were synthesized by a facile precipitation and dehydration methods. The synthesized samples were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-Visible diffuse reflectance spectroscopy (UV-Vis DRS), and photoluminescence (PL) techniques. Within various combinations of AgBr and ZnO components in the composites, 1AgBr/ZnO showed higher photocatalytic activity against 3-chlorophenol (3-CP). UV-Vis DRS spectra showed that the absorbance of AgBr/ZnO was higher than pure ZnO in the visible light region. The PL results showed that efficient inhibition of the generated electron/hole pairs has occurred during the degradation process due to the formation of heterojunctions. The forming of metallic Ag⁰ by photogenerated electrons, which captures Ag⁺ ions, could act as an interfacial charge transmission bridge in the AgBr/ZnO composite. These results provided an important insight into the plasmonic Ag particles to obtain an efficient visible light-driven photocatalyst. In addition, the possible mechanism of charge transfers and separation of electron/hole pairs were also evaluated in detail.

Application of Ag/AgBr/GdVO4 composite photocatalyst in wastewater treatment

Ag/AgBr/GdVO₄ composite photocatalysts were designed and synthesized in this paper. The physical and chemical structures, as well as optical properties of the synthesized composite were investigated via XRD, XPS, TEM, and UV-vis. It is found that the composite showed a ternary heterojunction structure of Ag, AgBr and GdVO₄. Meanwhile, it has a high intensity of light current, indicating its high separation efficiency of electron and hole. Photocatalytic oxidation of rhodamine B (RhB) under visible light irradiation was performed to investigate the activity of the Ag/AgBr/GdVO₄ composite. Result indicates that it shows excellent photocatalytic activity. Under visible light irradiation for 12min, about 80% of RhB (30μmol/L) was degraded. The degradation rate is estimated to be 0.253 min-1, which is three times higher than that of pure AgBr. The high photoactivity can be ascribed to the synergetic effect of AgBr, GdVO₄, and Ag nanoparticle in separation of electron-hole pairs.

Crystal transformation of 2D tungstic acid H2WO4 to WO3 for enhanced photocatalytic water oxidation

New photocatalytic materials for stable reduction and/or oxidization of water by harvesting a wider range of visible light are indispensable to achieve high practical efficiency in artificial photosynthesis. In this work, we prepared 2D WO₃·H₂O and WO₃ nanosheets by a one-pot hydrothermal method and sequent calcination, focusing on the effects of crystal transformation on band structure and photocatalytic performance for photocatalytic water oxidation in the presence of electron acceptors (Ag⁺) under simulated solar light irradiation. The as-prepared WO₃ nanosheets exhibit enhanced rate of photocatalytic water oxidation, which is 6.3 and 3.6 times higher than that of WO₃·H₂O nanosheets and commercial WO₃, respectively. It is demonstrated that the releasing of water molecules in the crystal phase of tungstic acid results in transformation of the crystal phase from orthorhombic WO₃·H₂O to monoclinic WO₃, significantly improving the activity of photocatalytic water oxidation in the presence of Ag⁺ because the shift-up of conduction band of WO₃ matches well with the electrode potential of Ag⁺/Ag(s), leading to efficient separation of photoinduced electrons and holes in pure WO₃ nanosheets.

An Au/AgBr–Ag heterostructure plasmonic photocatalyst with enhanced catalytic activity under visible light

An efficient bimetallic–semiconductor (Au/AgBr–Ag) plasmonic heterostructure with plasmon enhanced absorption and plasmonic sensitization for visible light induced photocatalysis.

One-pot synthesis of an AgBr/ZnO hierarchical structure with enhanced photocatalytic capacity

Hydrangea-like AgBr/ZnO photocatalysts with hierarchical structures and improved photocatalytic activity have been synthesized for the first time.

Facile synthesis of ternary Ag/AgBr-Ag(2)CO(3) hybrids with enhanced photocatalytic removal of elemental mercury driven by visible light

A novel technique for photocatalytic removal of elemental mercury (Hg(0)) using visible-light-driven Ag/AgBr-Ag2CO3 hybrids was proposed. The ternary Ag/AgBr-Ag2CO3 hybrids were synthesized by a simple modified co-precipitation method and characterized by N2 adsorption-desorption, scanning electron microscope (SEM), X-ray diffraction (XRD), UV-vis diffused reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) techniques. The effects of AgBr content, fluorescent lamp (FSL) irradiation, solution temperature, SO2 and NO on Hg(0) removal were investigated in detail. Furthermore, a possible reaction mechanism for higher Hg(0) removal was proposed, and the simultaneous removal of Hg(0), SO2 and NO was studied. The results showed that a high efficiency of Hg(0) removal was obtained by using Ag/AgBr-Ag2CO3 hybrids under fluorescent lamp irradiation. The AgBr content, FSL irradiation, solution temperature, and SO2 all exhibited significant effects on Hg(0) removal, while NO had slight effect on Hg(0) removal. The addition of Ca(OH)2 demonstrated a little impact on Hg(0) removal and could significantly improve the SO2-resistance performance of Ag/AgBr(0.7)-Ag2CO3 hybrid. The characterization results exhibited that hydroxyl radical (OH), superoxide radical (O2(-)), hole (h(+)), and Br(0), were reactive species responsible for removing Hg(0), and the h(+) played a key role in Hg(0) removal.

Tunable photocatalytic and photoelectric properties of I−-doped BiOBr photocatalyst: dramatic pH effect

Dramatic effect of synthesis pH was discovered for expediently tuning photocatalytic and photoelectric properties of I⁻-doped BiOBr photocatalyst.

In situ growth of Ag/Ag2O nanoparticles on g-C3N4 by a natural carbon nanodot-assisted green method for synergistic photocatalytic activity

Novel visible-light-driven Ag/Ag₂O@g-C₃N₄ hybrid materials were synthesized successfully via a green, facile hydrothermal treatment approach by reducing AgNO₃ with carbon nanodots for the first time.

Characterization and mechanism analysis of AgBr mixed cuboid WO3 rods with enhanced photocatalytic activity

The possible mechanisms for the formation of photocatalysts, enhanced photocatalytic properties and deactivation of the AgBr/m-WO₃ were investigated, respectively.

Universal degradation performance of a high-efficiency AgBr/Ag2CO3 photocatalyst under visible light and an insight into the reaction mechanism

A AgBr/Ag₂CO₃ photocatalyst exhibited excellent photocatalytic activity and stability under visible light and a two-stage photocatalytic mechanism was proposed.

La2Ti2O7 nanoplates decorated with Cu2ZnSnS4 nanoparticles for enhanced visible-light-driven photocatalytic activity

Novel Cu₂ZnSnS₄/La₂Ti₂O₇ hetero-junction photocatalysts with high visible-light-driven photocatalytic activities were achieved by a green process.

Hierarchically plasmonic photocatalysts of Ag/AgCl nanocrystals coupled with single-crystalline WO₃ nanoplates

The hierarchical photocatalysts of Ag/AgCl@plate-WO₃ have been synthesized by anchoring Ag/AgCl nanocrystals on the surfaces of single-crystalline WO₃ nanoplates that were obtained via an intercalation and topochemical approach. The heterogeneous precipitation process of the PVP-Ag⁺-WO₃ suspensions with a Cl⁻ solution added drop-wise was developed to synthesize AgCl@WO₃ composites, which were then photoreduced to form Ag/AgCl@WO₃ nanostructures in situ. WO₃ nanocrystals with various shapes (i.e., nanoplates, nanorods, and nanoparticles) were used as the substrates to synthesize Ag/AgCl@WO₃ photocatalysts, and the effects of the WO₃ contents and photoreduction times on their visible-light-driven photocatalytic performance were investigated. The techniques of TEM, SEM, XPS, EDS, XRD, N₂ adsorption-desorption and UV-vis DR spectra were used to characterize the compositions, phases and microstructures of the samples. The RhB aqueous solutions were used as the model system to estimate the photocatalytic performance of the as-obtained Ag/AgCl@WO₃ nanostructures under visible light (λ ≥ 420 nm) and sunlight. The results indicated that the hierarchical Ag/AgCl@plate-WO₃ photocatalyst has a higher photodegradation rate than Ag/AgCl, AgCl, AgCl@WO₃ and TiO₂ (P25). The contents and morphologies of the WO₃ substrates in the Ag/AgCl@plate-WO₃ photocatalysts have important effects on their photocatalytic performance. The related mechanisms for the enhancement in visible-light-driven photodegradation of RhB molecules were analyzed.

Visible light photocatalytic activity enhancement and mechanism of AgBr/Ag3PO4 hybrids for degradation of methyl orange

Novel AgBr/Ag(3)PO(4) hybrids were synthesized via an in situ anion-exchange method and characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS) and UV-vis diffuse reflectance spectroscopy (DRS). Under visible light (λ>420 nm), AgBr/Ag(3)PO(4) degraded methyl orange (MO) efficiently and displayed much higher photocatalytic activity than that of pure AgBr or Ag(3)PO(4). X-ray photoelectron spectroscopy (XPS) suggests that AgBr/Ag(3)PO(4) transformed to be Ag@AgBr/Ag(3)PO(4)@Ag system while remained good photocatalytic activity after 5 times of cycle experiments. In addition, the quenching effects of different scavengers proved that reactive OH and h(+) played the major role for the MO degradation. The photocatalytic activity enhancement of AgBr/Ag(3)PO(4) is closely related to the efficient separation of electron-hole pairs derived from the matching band potentials between AgBr and Ag(3)PO(4), as well as the good electron trapping role of Ag nanoparticles in situ formed on the surfaces of AgBr and Ag(3)PO(4) particles during the photocatalytic reaction.